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Based on density-functional theory calculations, the effects of cation compositions on electronic structures of In-Sn-Zn-O amorphous semiconductors were investigated. We considered various composition ratios of In, Sn, and Zn in O stoichiometric condition, and found that the conduction band minimum (CBM) energy level decreases and the valence band tail (VBT) energy level extent increases as the sum of In and Sn ratios (RIn+RSn) increases. The CBM lowering is attributed to the increased overlap of the In-5s and Sn-5s orbitals as the RIn+RSn increases, and correspondingly the electron effective masses (me*) are found to be reduced. The VBT increase is found to be due to the increased density of the In and Sn atoms, near which the O-2p inter-site ppσ* coupling is larger than that near the Zn atoms. The acute O-(In,Sn)-O angles are suggested to be structurally important, giving the stronger O-O ppσ* coupling.

The characterization of metallic electrodes in semiconducting devices with high spatial resolution has become increasingly important. In paticular, the evaluation of metal-metal interactions has been of vital importance in various technologies. Scanning force microscopy (SFM) enables us to observe surface topographies on a nanometer scale along with local mechanical properties such as friction force without any special surface treatment. It has been difficult to obtain high resolutions using conventional methods such as Auger electron spectroscopy, because of their beam size. In this study, we demonstrated the possibility of two dimensional metal mapping of mechanical properties by magnetic force controlled-atomic force microscopy (MFC-AFM), and a new force modulation method to determine the two metals. The Au-Ni system of metallic electrodes is one such example. Here, we also attempted to differentiate mapping of compositional inorganic materials such as Au islands, deposited on a flat Ni substrate. The Hertzian radius is 13.2 nm for Ni, and 23 nm for Au. We estimate the tip-sample deformation to be 2.9 nm for Au, and 0.97 nm for Ni, respectively.

In this paper, we have compared amorphous InGaZnO (a-IGZO) thin-film transistor (TFT) with the nano-crystalline embedded-IGZO (Nc-embedded-IGZO) TFT fabricated by solid-phase crystallization (SPC) technique. The field effect mobility (μFE) of Nc-embedded-IGZO TFT was 2.37 cm 2 /Vs and the subthreshold slope (S-factor) was 0.83 V/decade, which showed lower performance than those of a-IGZO TFT (μFE of a-IGZO was 9.67 cm 2 /Vs and S-factor was 0.19 V/decade). This results originated from generation of oxygen vacancies in oxide semiconductor and interface between gate insulator and semiconductor due to high temperature annealing process. However, the threshold voltage shift (△VTH) of Nc-embedded-IGZO TFT was 0.5 V, which showed 1 V less shift than that of a-IGZO TFT under constant current stress during 10 5 s. This was because there were additionally less increase of interface trap charges in Nc-embedded-IGZO TFT than a-IGZO TFT.

The dominant mechanism of the negative bias stress (NBS)-induced instability is investigated not to be a change in the subgap DOS but a change in the parasitic resistance caused by the reduced Schottky barrier of the metal contacts. This was verified by the extracted source/drain resistance and TCAD simulation.